Heaters are a critical component of a healthy aquarium, but they serve a straightforward purpose and are not often the fanciest or feature-filled component in your setup. There are a few different aquarium heater types, including submersible and external models, which are further differentiated by their wattage and how many gallons they can consistently heat.
In addition to whatever heater you choose, you must always have a reliable thermometer in the tank to ensure your heater is working correctly. A faulty heater may not be very obvious and even small temperature fluctuations can have disastrous consequences.
As Dr. Jessica Fox, a Certified Aquatic Veterinarian, explains,
“The temperature range of your tank inhabitants will not all be the same. Some fish and invertebrates are very hardy to temperature changes, while others can get sick quickly," Dr. Jessica Fox, a Certified Aquatic Veterinarian, told The Spruce Pets. "Maintaining the correct temperature range in your tank is critical to ensuring your fish live long and healthy lives.”
The best aquarium heater is the Orlushy Submersible, for its reliability and easy-to-set controls. Plus, it comes with a separate digital thermometer so you can doublecheck that its accurately heating your tank (or you could pair it with one of our favorite thermometers).
Best Overall
Orlushy Submersible Aquarium Heater
Variety of sizes
Big, friendly knob makes it easy to adjust the temperature
Easy to install
Affordable and reliable
Smaller models—for tanks less than 10 gallons—are less accurate at holding a consistent temperature
The Orlushy Submersible Aquarium Heater provides any fish keeper with a reliable thermometer with a solid outer casing and full adjustability. This product line comes in a variety of sizes, accommodating 1-6 gallons with its 25W heater all the way up to 75 gallons with its 500W heater. Two suction cups are provided to keep your heater secured and away from the main area of your tank. It also comes with a digital thermometer to ensure your heater is working correctly.
What we appreciate about this model is its ease of use and clear functions. Its size variety makes it very friendly for most pet fish tank sizes, while keeping a good price point. Overall, the Orlushy Submersible Aquarium Heater is a great choice for your aquarium, no matter what the tropical species or size of tank.
Temperature Range: 68-89 F | Gallon Range: 1-75 gallons | Wattage: 25W, 50W, 100W, 150W, 200W, 300W, 500W | Cord Length: 6 feet
Best for Large Tanks
Fluval E Electronic Heater
More consistent heating
Fully adjustable (to 0.5 degrees)
Color display
Reliable once installed, but fragile enough that it can be damaged during shipping
If you have a lot of water to heat, then you need the Fluval E300 Advanced Electronic Heater. This 300W heater is able to heat up to 100 gallons of water to 69 to 93F. Designed specifically for larger tanks, this heater has an easy to read digital display with corresponding color codes to ensure your water temperature is within the proper range. The unit is fully submersible with a protective outer shell to keep fish and invertebrates from getting too close. Yes, it is the most expensive heater on this list, but there is a lot of technology going into a heater designed to keep a large volume of water heated consistently.
Temperature Range: 68 to 93 F | Gallon Range: 75 to 100 gallons | Wattage: 300W | Cord Length: 6 feet
Best for Small Tanks
HITOP Adjustable Aquarium Heater
Adjustable
Easy to use
Inexpensive
Takes up tank space
Hard to keep consistent temperature
Small tanks are the hardest to heat consistently, but the HITOP Adjustable Aquarium Heater has taken this into account with even its smallest model. The 25W model is easy to set up and fully adjustable to your fishes’ preferred temperature. If you need something a little bit bigger, there is a full range of sizes for your smaller aquariums. Very easy to install and use, the HITOP Adjustable Aquarium heater is a good choice for your smaller aquariums.
Temperature Range: 68 to 93 F | Gallon Range: 5 to 10 gallons | Wattage: 25W | Cord Length: 4.9 feet
Best for Beta Fish
HiTauing Small Aquarium Heater
Minimal tank space needs
Adjustable
External temperature control
Hard to follow instructions
Looking for a heater for your betta fish tank? Then the HiTauing Small Aquarium Heater is an excellent choice. With its slim profile, it takes up considerably less tank room and you can adjust the temperature from outside the tank. This makes the HiTauing Heater a great choice for smaller betta tanks and ensures proper tank temperature to keep your betta healthy.
Temperature Range: 59 to 93 F | Gallon Range: 5 to 10 gallons | Wattage: 15W | Cord Length: 4.4 feet
Best Nano
FREESEA Fish Tank Submersible Heater
External controls allow for smaller internal profile
Internal shape takes up less room
Easy to read temperature
Wide temperature fluctuation (3-4 F) possible
Small, nano tanks requiring heat should check out the Freesea 50W Mini Aquarium Heater. Unlike most tube-shaped heaters, this flat disk takes up less of your valuable tank space and can provide quite a bit of heat for a small space. This model comes with an external adjustable temperature range and has an easy to read digital display. Larger models are available if you plan on upgrading your tank from nano to medium.
Temperature Range: 59 to 93 F | Gallon Range: 1 to 10 gallons | Wattage: 50W | Cord Length: 3.5 feet
Best Budget
Tetra HT Submersible Aquarium Heater
Inexpensive
Multiple size ranges
Easy to install
Not adjustable
Only one attachment
Wide temperature fluctuation possible (3-4 F)
The Tetra Submersible Aquarium Heater is a line of heaters that very inexpensive, but also do not have many features, such as adjustable temperature settings, and only come with one suction cup attachment. However, if you need a heater and have a small budget, this heater will reliably keep your fish at a comfortable temperature.
Temperature Range: 78 F | Gallon Range: 2 to 10 gallons | Wattage: 100W | Cord Length: 6 feet
Best Heater Guard
Tnfeeon Fish Tank Heater Protective Case
Customizable size
Works with many brands of heaters
Better mounting capabilities
Unnecessary for many heaters
If you have to protect your fishes’ or invertebrates’ from your heating element, then consider the Tnfeeon Fish Tank Heater Protective Case. What is great about this heater case is that you can customize the length to almost any standard heater brand or model. This is a great addition to heaters that won’t stay put and need some extra stability or have unruly tankmates. Includes 6 sections to accommodate 25W to 1000W heaters and 2 strong suction cups for solid attachments.
Overall, the Orlushy Submersible Aquarium Heater could be the only fish tank heater on this list for most hobby aquarium owners. All of the others have their individual virtues, but for the price point, ease of installation, variation of sizes and reliability, the Orlushy can’t be beat. Be sure to choose the size that fits your aquarium and your fish will soon be enjoying their tropical home!
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Does an aquarium heater need to be fully submerged?
The amount of your heater that needs to be submerged will depend on the model and manufacturer. Most aquarium heaters are designed to be fully submerged, but this is not always the case. Please read your installation instructions carefully in order to ensure proper function for your heater and always use a thermometer to confirm your heater is operating correctly.
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How many watts should I have per gallon?
Wattage per gallon of water will vary by make and model. All heaters will have a gallon range on their packaging.
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Can an aquarium heater burn my fish?
When functioning properly, your heater should not be capable of burning your fish. Many tropical fish, including bettas, will enjoy resting directly next to the heater to enhance their immunity and metabolism. If your heater is not operating correctly, it can potentially burn your fish, but it is very unlikely.
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How do I know if my heater is working properly?
The best way to ensure your heater is working correctly is to carefully read the instructions upon installation and use a reliable thermometer in your tank. Do not assume your heater is 100% foolproof. Only by using a reliable secondary thermometer, like one of these, can you save your fish tank from disaster.
Why Trust The Spruce?
With over 10 years experience as a pet fish veterinarian, author Dr. Jessie Sanders has significant experience when it comes to fish tank components. In addition to working with hundreds of fish tank clients, she also owned a fish retail store, specializing in only the best products for fish, several of which are present on this list.